Method of heating and forming tubular bodies



` June 22, 194s,

' w. c. HEATH 2,322,444 METHOD OF HEATING AND FORMING TUBULAR BODIES I Filed Sept. 14, 1942 1N VENTOR.

ATTORNEY Patented June 22, 1943 METHOD F HEATING AND FORMING TUBULAR BODIES WilliamC. Heath, Shorewood, Wis., assignor to A. O. Smith Corporation, Milwaukee, Wis., a corporation of New York Application September 14, 1942, Serial No. 458,229

2 Claims.

This invention relates to a method of heating and forming tubular bodies and constitutes an improvement upon the method set forth in the application of Sven Westin and Axel Westin, Serial No. 376,669, filed January 30, 1941, for improvement in Method of treating metallic bodies." In this method, the end of a rotating tube is fed into a die cavity formed by circumferentially spaced electrode dies, wherein the heating current passes through successive portions o`f the blank and the latter is formed simultaneously with its softening.

Heretofore, in the application of the Westin process, set forth in the application specified above, to the forming of thick tubes-as in the making of large bomb casings and in the reduction of such tubes in diameter it has been found that certain tolerances of manufacture cause difficulty. The thick-walled blanks are -never perfectly cylindrical on the outside and certain longitudinal sections constitute radial high spots which engage the electrode dies first. The thickness and rigidity of the Wall prevents the giving of the blank in the region of the high spots and as a result certain areas Vof the blank do not engage the electrodes; at least such engagement as may occur is not sufficiently uni form in pressure to effect the desired uniformity of heating.

The high spots referred to become hot before the low areas. Sometimes this results in the hotter almost liquid metal at the surface of the high spot running or being draggedby the friction of the die over the lower area between two high spots to produce what may be called a fold. Such folds may appear in the finished product and constitute a defect therein. At other times the differences in temperature between diil'erent portions of the blank may cause an actual tearing apart of the blank.

' The object of the present invention is to overcome these dilculties and to provide any improved method for applying the Westin process to thick-walled blanks and blanks of slightly irregular shape. In carrying out the invention, the portion of the blank to be formed is subjected to apreliminary heating operation either prior to or simultaneously with the feeding of the blank into engagement with the dies. This preliminary heating is preferably of suicient extent to soften the metal throughout its thickness so that the walls of the blank will give and conform more readily to the dies as the blank engages the same.

The invention is diagrammatically illustrated by the accompanying drawing in which:

Figure l is a side elevation partly in section of one form of apparatus for carrying out the invention and with the blank about to be entered in the dies;

Fig. 2 is -a similar view showing the blank partially entered into the dies; and

Fig. 3 is a transverse section taken on line 3-3 of Fig. 1.

As illustrated in the drawing, the thick-walled tubular blank I is rotated and moved axially forward by means of a rotating chuckl gripping the end thereof and mounted on a shaft 3 journaled in an upright standard 4 which is moved axially along a base support 5 by means of the hydraulic cylinder and piston 6. An electric motor 'I on the standard I drives the chuck 2 by suitablegearing 8.

The forward end of the blank I passes first through a series of gas flames from burners 9 arranged around the circumference of the blank and directed to impinge upon the blank to heat the portion to be formed to a state of relative softness. The rotating of the blank insures substantial uniformity of heating thereof in this preliminary operation.

The forward end of the blank next enters the die cavity provided between the electrode dies III and II. The dies are complementary, similar to those set forth in theapplication above referred to, and are connected by leads I2 t0 a suitable source I3 of heating current to effect heating of the blank by its lresistance to the flow of current y between the electrodes.

The rotation of the blank I in the dies I0 and I I and the longitudinal axial feeding of the blank into the dies effects a simultaneous heating and forming off thevsuccessive circumferential portions of the blank as the same are pressed into engagement with the electrode dies.

'I'he preliminary heating step increases the initial resistance of the blank to the iiow -of the heating current and makes the latter more effec'- v pend upon the metal of the blank, it being preferable to initially heat the portion of the blank to be formed to a low forging temperature therefor. Various embodiments of the invention may be employed within the scope of the accompanying claims.

I claim:

1. In the method of electric heating and Iorrning an article in circular shape by the application of electrode forming dies in engagement with the blank being formed, said dies and blank being relatively rotated and fed axially to provide a progressive recurrent heating and forming of successive adjacent portions of the blank, the preheating ot longitudinally adjacent circumierential portions of the blank as the same are fed to the dies and prior to contact of suchv 

